if you don't want to take the computer out to do fairly ambitious live recordings, where you might need a few mics, then there is no real reason for a really expensive soundcard with many inputs. additionally if the sound card is not dealing with many audio streams then USB becomes an option.
Also you can also get some capacitor mics such as the rodeNT3 that you can put batteries in - so phantom power is not essential, and you still have the quality of a reasonable condeser mic and full portability with no need for a mains supply.
do you plan to mix everything down in the PC? if so then you will only need a stereo output. if you wish to use some outboard gear then you may need some more
The partitioning is definately a good idea.
I wasn't meaning that only one of the AMD or pentium has floating point capabilities, rather the issue is how many floating point operations per second that they can perform, check this site;
another thing to consider is what sample rate & bit depth you want to be able to acheive with your sound card, i.e. how much quality are you looking for.